The present invention relates to a fuel injection system for mixture compressing, externally ignited internal combustion engines, and more particularly to such a system including fuel injection valves, and a fuel distribution unit with fuel metering valves which determine the fuel quantity flowing into the injection valves by jointly changing their flow cross section. The metering process in such a system occurs at a constant pressure difference. Disposed in each fuel flow path downstream of the fuel-metering valves is a valve, whose flow cross section can be changed by a flexible member. The flexible member for each valve separates two chambers in the valve with the pressure in the first chamber of each valve being the fuel pressure prevailing downstream of the metering valve. This pressure acts on the flexible member in the opening direction of the valves.
Such fuel injection systems are designed for the purpose of using the magnitude of a setting parameter which acts on the fuel metering valve and which corresponds to the operational conditions of the internal combustion engine in order to achieve an appropriate change in the flow cross section of the downstream valves and also, with the aid of as constant a pressure gradient as possible across this flow cross section, to achieve a constantly precise metering of fuel corresponding to the particular open cross section of the downstream valves and one which is independent of the pressures prevailing before and behind this metering location.
In a known fuel injection system of this kind, the fuel for the individual cylinders of the internal combustion engine is metered out in common by a fuel metering valve. The fuel metering valve has a different control slit for each engine cylinder and a control slide having a control edge operatively associated with the different control slits. In this system, the fuel metering takes place at a pressure difference which is held constant by equal pressure valves. The pressure difference can, however, be changed in dependence on engine parameters, and the control pressure acting on the equal pressure valves is adjustable by means of a control pressure valve.
A fuel injection system so designed requires both a supply circuit and a control pressure circuit. Furthermore, a supplementary control pressure valve is required for each cylinder of the internal combustion engine in addition to the equal pressure valves.